Mark Tilden is best known as the creator of BEAM robotics and the creator of Bio-bugs and Robosapien. He used to work for the Los Alamos National Laboratory, although now he spends his time creating robots for WowWee Toys.
Most of his robots use simple circuits to create complex behaviours, in the belief that you don't need a large computer brain to accomplish the basics.
He's also big on solar cell powered robots and things built out of junk. One of his coolest robots was a walker named Walkman, built out of old Sony Walkman motors. Unfortunately, Walkman escaped from the lab and hasn't been seen since (or perhaps he was stolen, it's hard to say with semi-intelligent automatons).
Tilden also developed something known as a Robot Jurassic Park for his little creations to play around in. Reportedly, some of the roller bots were known to snap the necks of the Beamants, which led them to be known as the velociraptors of the park.